US3691481A

US3691481A - Negative resistance element

Info

Publication number: US3691481A
Application number: US167410A
Authority: US
Inventors: Shoei Kataoka; Hiroshi Tateno; Hiroyuki Fujisada; Mitsuo Kawashima; Yasuo Komamiya; Hideo Yamada
Original assignee: Agency of Industrial Science and Technology; INTERN TRADE AND IND JAPAN
Current assignee: National Institute of Advanced Industrial Science and Technology AIST; INTERN TRADE AND IND JAPAN
Priority date: 1967-08-22
Filing date: 1971-07-29
Publication date: 1972-09-12
Anticipated expiration: 1989-09-12

Abstract

Occurrence of high field domain in the conventional Gunn diode is prevented by covering a solid body such as a semiconductor element partially or wholly by a dielectric member or by a control element such as a metallic layer coupled reactively with the solid body through a dielectric member, whereby a solid state element having a negative differential conductivity is obtained. Such a type of negative-resistance solid state element, together with its various modes of embodimental construction disclosed herein, affords a superior solid state element which is applicable to amplifiers, oscillators, logic memories, and the like of millimeter or submillimeter bands.

Description

United States Patent Kataokaet al.

1151 3,691,481 14 1 Sept. 12,1972

1541 NEGATIVE RESISTANCE ELEMENT Inventors:

Assignee:

Filed:

Appl. No.:

Shoei Kataoka, Hiroshi, Tateno, both of Tokyo-to; Hiroyuki Fujisada, Tokyo-to; Mitsuo Kawashima, Tokyo-to; Yasuo Komamiya, Hideo Yamada, Yokohama, all of Japan Kogyo Gijutsuin (a/k/ a Agency of Industrial Science and Technology, Ministry of International Trade and Industry, Japanese Government), Tokyo-to, J apan July 29, 1971 Related US. Application Data Continuation-in-part of Ser. No. 776,292, Aug. 20, 1968, abandoned.

Foreign Application Priority Data Aug. 22, 1967 Nov. 27, 1967 Nov. 27, 1967 Nov. 27, 1967 Nov. 27, 1967 Japan ..42/53488 Japan ..42/75628 Japan ..42/75629 Japan ..42/75630 Japan ..42/75631 US. Cl ..331/107 G, 307/299, 317/234 V,

330/5 Int. Cl. ..H03b 7/14 Field of Search..............33l/l07 G; 3 l7/234 V;

[56] References Cited UNITED STATES PATEN S 3,365,583. 1/19 8 Gunn ..317/234 3,434,003 3/1969 Sandbank ..317/234 3,439,236 4/1969 131161161 ..317/234 3,443,169 5/1969 Foxelletal ..317/234 3,452,222 6/1969 Shoji ..317 234 3,462,617 8/1969 Shoji ..317/234 Primary Examiner-Roy Lake Assistant Examiner-Darwin R. Hostetter Attorney-Robert E. Burns et al.

[57] ABSTRACT plifiers, oscillators, logic memories, and the like of millimeter or submillimeter bands.

31 Claims, 77 Drawing Figures 5 4, Ag i VII PATENTEDSEP 12 I912 3.691 .48 1

SHEET UlUF 18 FlG.1(a)

FIG. Nb) 8 ggF STRENGTH OF ELECTRIC FIELD .1(c) a F 6 FIG. He)

2/ 3 1 E FIG.1(d) g 8 o i 0 --TIME r f PATENTED SEP 12 m2 SHEET 02 0F 18 FlG.2(a)

FIG. 2(b) FIG. 3(b) FIG. 3(0) PATENTEDSEP 12 I972 SHEET USUF 18 FIG. 5(0) CRITICAL ELECTRIC FIELD APPLIED ELECTRIC FIELD 3mm 258d V V -TIME PATENTED I973 3.691.481

saw on or 18 FIG. 5(0) FIG. 5(d) 1 V V V L FIG. 6(a) 5 6 5 J; 4 \K 4K i ELECTRIC FIELD AMPLIFIED OUTPUT VOLTAGE I FATENTED SEP 12 i972- SHEET DSUF 18 FlG.6(b)

22' TIME 9 E g H FIG. 6(c) 2 g? A A TIME V\/ O I 7 FIG. 7(a) t E CRITICAL ELECTRIC 9 5 FIELD CATHODE ANODE PATENTED E 12 m2 3.691; 481

SHEET UBUF 18 FlG.7(b)

F|G.7(c) 5 FIG. 7(a) C) FIG. 7(e) v PATENTEDSEP 12 m2 SHEET 07UF 18 FIG. 7(i) PATENTEDSEPIZIQTZ I 3.691.481

SHEET USUF 18 F|G.8(a)

FIG. 8(0) PATENTEDSEPIZ m V 3.691; 481

SHEET 10 0F 18 4 FIG. 9(

FIG. 9(b) CURRENT O VOLTAGE PATENTEDSEP 12 I912 3.69 1 481 SHEET 120F 18 9 4 t Ila g FIG. 9(k) 4 9 4 Q\ \IVLM\\$\\\\I FIG. 9(1) FIG.9(m)' VOLTAGE FIG. |l(a) i INPUT OUT PUT U FIG. ll(b) it INPUT D OUT PUT FIG. l|(c) |N PUT I OUT PUT PATENTEDsEP 12 1912 3.691.481

' sum 180F 18 0 4 FIG. l3(b) PNENTEDSEPIZ I912 3.691.481

SHEET l'IUF 18 FIG. |4(u) FIG. l4(b) FIG. l4(c) PATENTEDSEPI l9 SHEET 18oF 18 I 3 481 4 [III B FIG. 15m

FIG. l5(9) NEGATIVE RESISTANCE ELEMENT REFERENCE TO RELATED APPLICATION This application is a continuation-in-part of our copending application Ser. No. 776,292 filed Aug. 20, 1968, and now abandoned for NEGATIVE RE- GISTANCE ELEMENT AND ITS APPLICATION.

BACKGROUND OF THE INVENTION This invention relates to a novel type of negative-resistance solid state element, and more particularly to such type of element that exhibits negative differential conductivity upon application thereto of a high electric field and to applications thereof.

Heretofore, negative-resistance elements such as the so-called Ezaki diode, which utilize a tunnel effect of semiconductors, have been known. However, in the Ezaki diode, since the negative resistance is obtained at the P-N junction of the semiconductive substances, the negative differential conductivity is exhibited only for a specific polarity, and because of the capacitance existing at the junction point, the element cannot be used at frequencies higher than GI-Iz. These features together with its limited output power constitute the drawbacks of this type of diode.

The so-called Gunn diode is also known, wherein a semiconductive material such as GaAs which has two valleys in its conduction band is employed. When a 1 high electric field is applied across such an element, electrons are transferred from the lower energy valley to the higher energy valley, and because mobility of the electrons in the higher energy valley is less than the mobility in the lower energy valley, the average speed of electrons decreases with increase in electric field. When the intensity of the internal electric field applied from outside as described above exceeds a critical value (about 3,000 V/cm), a high field domain is created near the cathode, which is thereafter shifted to the anode by the action of the applied electric field. When the high field domain reaches the anode, it disappears at once, and an impulsive current is caused to flow through the semiconductive substance because of the disappearance of the high field domain. Following this disappearance, new high field domain is created near the cathode and the same sequences mentioned above are repeated at a frequency determined by the length ofthe element.

This typs of solid state element can be utilized in generating high-frequency oscillation of a frequency determined by l/v wherein Z designates the length of the element, and v,, designates the velocity of the high field domain. Considering the fact that the velocity v of the high field domain is about 10 cm/sec., it is apparent from this formula that the length of the element must be minimized to an extremely short value (of the order of several microns) if it is desired to obtain micro-wave or millimeter wavelength.

Despite various efforts to obtain still higher frequencies than those described above, it has been found that the practical limitation exists around several tens of GHz, and the resultant oscillation output is rapidly decreased with increase in the frequency. Such features together with its excessively narrow frequency band constitute drawbacks of the Gunn type solid element.

The so-called LSA diode is also known. lt is believed that with this type of diode further increase in the oscillation frequency can be attained with a moderate efficiency. However, in this case, since the biasing electric field must be higher than twice the value of the Gunn diode, the semiconductive material must be of extremely uniform quality, and, moreover, as there is a limitation in the relationship between the electron density and frequency, these are other features constituting the shortcomings of the LSA diode.

We have found that, if one or whole part of the surface of a semiconductive element of, for instance, GaAs, is covered by a dielectric layer or a metallic layer which is reactively coupled with the semiconductive element through an intermediate dielectric thin layer, the occurrence of the high field domain at the time when a high electric field is applied thereacross can be prevented, and a novel condition which might be called negative-differential resistance characteristic or negative differential conductivity can be obtained.

SUMMARY OF THE INVENTION With the above-described discovery in view, the principal object of the present invention is to provide a novel type negative-resistance solid state element, whereby the afore-described difficulties in conventional elements are substantially reduced or eliminated.

Another object of the present invention is to provide a novel type of solid state element, which is operable under an entirely new principle completely differing from those of the conventional elements, whereby oscillation in a range of from extremely low frequency to 300 Gl-Iz can be obtained.

Still another object of the present invention is to provide a novel type of solid state element, which is operable under an entirely new principle and having a completely new configuration, whereby a much improved negative differential conductivity is obtained, and the element is made applicable to a wide variety of applications such as in oscillation, amplification, and logic memory.

The above stated objects and other objects of the present invention can be accomplished by a novel type of negative-resistance solid state element which comprises: a semiconductive element showing negative differential conductivity in a high electric field and having at least two end portions; a plurality of electrodes ohmically attached to the semiconductive element at least two end portions for application of an electric voltage causing production of said high electric field; and a dielectric member or this dielectric member and at least one control element which cover at least one part of said semiconductor element, said control element being reactively coupled with said semiconductor element through said dielectric member, whereby the high field domain created in the semiconductive element is suppressed at the time when a high electric voltage is applied across the electrodes and a negative differential conductivity is created within the bulk of the semiconductive element.

The nature, principle, and advantages of the present invention will become more apparent from the following description and appended claims, when considered in conjunction with the accompanying drawings, wherein the same reference numerals refer to like or corresponding parts throughout the several views.

Claims

1. A negative-resistance solid state element comprising: a solid body composed of semiconductor material having at least two ends and exhibiting a negative differential conductivity when placed in a high electric field; an electrode ohmically attached to each of said ends; means for applying a voltage across said electrodes; and at least one dielectric member covering at least one surface portion of said solid body and having a permittivity sufficiently higher than that of said solid body to effectively shortcircuit space charges created in said solid body during the application of said voltage thereby preventing high electric field domains from nucleating therein and establishing a negative resistance across said electrodes.

2. A negative resistance solid state element comprising: a solid body composed of semiconductor material having at least two ends and exhibiting a negative differential conductivity when placed in a high electric field; an electrode ohmically attached to each of said ends; means for applying a voltage across said electrodes; at least one dielectric member covering at least one surface portion of said solid body; and at least one metal layer provided on said dielectric member cooperative therewith, capacitance created by said dielectric member and the metal layer being effective to shortcircuit space charges created in said solid body during the application of said voltage, thereby preventing high electric field domains from nucleating therein and establishing a negative resistance across said electrodes.

3. A negative-resistance solid state element according to claim 1, in which the cross-sectional area of said solid body at portions near said electrodes differs from the cross-sectional area at remaining portions thereof.

4. A negative-resistance solid state element according to claim 1, wherein the cross-sectional area of said solid body is enlarged at regions near said electrodes in comparison with the cross-sectional area at remaining regions thereof.

5. A negative-resistance solid state element according to claim 1, wherein said solid body is provided with an input electrode disposed near one said electrode and an output electrode disposed near the other of said electrodes.

6. A negative-resistance solid state element as claimed in claim 1, further including at least one control element ohmically attached to said solid body.

7. A negative-resistance solid state element as claimed in claim 2, further comprising at least one control element capacitively attached to said solid body.

8. A negative-resistance solid state element as claimed in claim 2, wherein a pair of output electrodes are provided on the surface of the solid body near the two ends thereof, said output electrodes being reactively coupled with said solid body.

9. A negative-resistance solid state element as claimed in claim 1, wherein the cross-sectional area of one end portion of said solid body is enlarged in comparison with the remaining portions thereof.

10. A negative-resistance solid state element as claimed in claim 2, wherein the cross-sectional area of said solid body is enlarged at both said ends in comparison with the remaining portions thereof.

11. A negative-resistance device consisting of a plurality of laminated negative-resistance solid state elements, each comprising: a solid body composed of semiconductor material having at least two ends and exhibiting a negative differential conductivity when placed in a high electric field; electrodes ohmically attached to said ends; means for applying a voltage across said electrodes; and at least one dielectric member covering at least one surface portion of said solid body to effectively shortcircuit space charges created in said solid body during the application of said high electrIc field thereby preventing high electric field domains from nucleating therein and establishing a negative resistance across said electrodes.

12. A negative-resistance device consisting of a plurality of laminated negative-resistance solid state elements, each comprising: a solid body composed of semiconductor material having at least two ends and exhibiting a negative differential conductivity when placed in a high electric field; electrodes ohmically attached to said ends; means for applying a voltage across said electrodes; at least one dielectric member covering at least one surface part of said solid body to effectively shortcircuit space charges created in said solid body during the application of said voltage thereby preventing high electric field domains from nucleating therein and establishing a negative resistance across said electrodes; and at least one metal layer superposed on said dielectric member coacting therewith to effectively suppress high electric field domains in said solid body.

13. A negative-resistance solid state element according to claim 1, wherein a plurality of dielectric members are provided on said solid body with a small air gap therebetween in a direction perpendicular to the direction of current flow in said solid body.

14. A negative-resistance solid state element according to claim 2, wherein a plurality of dielectric members and a plurality of metal layers are provided on said solid body with a small air gap therebetween in a direction perpendicular to the direction of current flow in said solid body.

15. A negative-resistance solid state element according to claim 2, wherein a plurality of metal layers are provided on said dielectric layer with a small air gap therebetween in a direction perpendicular to the direction of current flow in said solid body.

16. A negative-resistance solid state element according to claim 1, wherein the dielectric member extends sufficiently to cover the junction portions between said solid body and said ohmically attached electrodes.

17. A negative-resistance solid state element according to claim 2, wherein said dielectric member and said metal layer extend lengthwise sufficiently to cover the junction portions between said solid body and said ohmically attached electrodes.

18. A negative-resistance solid state element according to claim 2, in which the cross-sectional area of said solid body at portions near said electrodes differs from the cross-sectional area at remaining portions thereof.

19. A negative-resistance solid state element according to claim 2, wherein the cross-sectional area of said solid body is enlarged at its regions near the electrodes in comparison with the rest of the regions thereof.

20. A negative-resistance solid state element according to claim 2, wherein said solid body is provided with an input electrode disposed near the cathode thereof and with an output electrode disposed near the anode thereof.

21. A negative-resistance solid state element as claimed in claim 2, wherein the cross-sectional area of one end portion of the solid body near the anode is enlarged in comparison with the rest of the portions thereof.

22. A negative-resistance solid state element as claimed in claim 2, wherein the cross-sectional area of both end portions of the solid body near the anode and cathode is enlarged in comparison with the rest of the portions thereof.

23. A negative-resistance solid state device comprising: an elongated semiconductor body having a pair of longitudinally spaced-apart ends operable in a first mode to develop therein travelling electric field domains successively travelling from one said end to the other said end and a second mode exhibiting a negative differential conductivity; an electrode ohmically affixed to each said end, means for applying a voltage during operation of the device between said electrodes effective to bias said elongated semiconductor body into said first mode; and suppressing means for effectively suppressing said travelliNg electric field domains to convert said elongated semiconductor body into said second mode.

24. A device according to claim 23, wherein said suppressing means comprises a dielectric member having a permittivity higher than that of said semiconductor body disposed around at least a portion of the peripheral surface of said elongated semiconductor body.

25. A device according to claim 24, wherein said dielectric member extends longitudinally over at least a major portion of the length of said elongated semiconductor body.

26. A device according to claim 25, wherein said elongated semiconductor body has a different cross-sectional area near each said end than at remaining portions thereof.

27. A device according to claim 25, including a metallic layer superposed on the exterior of said dielectric member reactively coupled with said semiconductor body through said dielectric member.

28. A device according to claim 25, further including another electrode ohmically connected to said semiconductor body between said spaced-apart ends.

29. A device according to claim 25, further including another electrode reactively coupled with said semiconductor body at a location between said spaced-apart ends.

30. A negative-resistance solid state element as claimed in claim 1, further including at least one control element capacitively attached to said solid body.

31. A negative-resistance solid state element as claimed in claim 2, further including at least one control element ohmically attached to said solid body.